Alario became a member of the Louisiana House of Representatives in 1972. As a Representative, Alario was the chairman of the Appropriations, House Executive, and Ways and Means committees. He also served as chairman to the Joint Legislative Committee on the Budget and the Joint Legislative Committee on Capital Outlay. He was a member of the House Commerce, House and Governmental Affairs, Legislative Budgetary Control, Municipal, Parochial, and Cultural Affairs, Natural Resources, Judiciary B, and Judicial committees.[2][3]

He was selected by GovernorEdwin Edwards as Speaker of the House twice, from 1984 to 1988 and from 1992 to 1996.[2] As the House Speaker, Alario was described by a colleague, Ron Gomez of Lafayette, as "a master of adding just the right degree of levity to defuse almost any potentially explosive situation."[5] In 1986, Alario removed Representative Kevin P. Reilly, Sr., of Baton Rouge from the chairmanship of the House Appropriations Committee after thirteen years of service when Reilly, an unsuccessful candidate for state treasurer the following year, criticized Governor Edwards.[6]

With the election of Buddy Roemer as governor, Alario was replaced as Speaker by Jimmy N. Dimos of Monroe. Ron Gomez explained that Alario and Senate President Sammy Nunez of Chalmette nevertheless attempted to maintain their leadership posts. He explained: "Alario immediately had the backing of organized labor, the black caucus, many member from the New Orleans and Jefferson Parish delegations and a healthy number of other House members whom he had helped and to whom he had ingratiated himself over the years."[7]

Overall, Alario served nine terms in the House of Representatives before being term limited from the body in 2007.[2]

Ultimately, only one of the thirty-nine senators, freshman Republican Barrow Peacock of Shreveport, voted against the Alario selection.[9] Jindal had supported Peacock's Republican rival, term-limited State Representative Jane H. Smith of Bossier City, in the general election for the District 37 seat held on November 19, 2011.[10]